Do u agree that Autocad will lose its credibility in coming future because of the emergence of new 3D softwares, even from autodesk (Revit-MEP)?

Well, I think2D will always be2D and3D will always be3D, people prefer2D on autocad and3D on3Dsmax, we'll never stop making2D drawings as they're very important to read and understand.
We'll always need programs to make our2D and3D also4D drawings.
I think While other programs keep popping up for our field and needs, Autocad will keep developing to compete especially that it's a successful and very popular program because it's easy and flexible.
Autodesk is a big company and it owns all the huge graphic projects and applications, so they'll never neglect the Autocad development because it's bringing a great income on them.
The architects will make their choices and we all look for the easiest and fastest means, don't we?

Soon Revit shall take a lead. Most of the organizations are moving into Revit including approving bodies.

Its not that AutoCAD shall loose credibility. Rivet shall get more credit soon. That all.

3D is better for accurate designs and also it can do auto size selections etc. Also mistakes & reworks can reduce considerably. For this reason, Revit is appreciated. 

Even though Autocad can be used for3D,it is widely used in making2D dwgs,but nowadays Client/Designers are focusing on more Intelligent3D software's like REVIT MEP in construction for example,were they can review ,analysis their design and many more ,also conversion to2D from these software s added advantage...
So I think,Yes in coming future- will be for3D softwares,,

Considering AutoCad is the pioneer Tool for all Architectural, engineering, manufacturing Fields, your answer for now would be No. AutoCad by itself is100 % accurate, therefore will always be credible. Since Revit is now an Autodesk product, they will always be separate products on offer.

no autoCAD will stil most engineering program sophisticated because thay used a profisionals computar engineers so I dont think that thay will stop sophisticate

AUTOCAD is the origin of the Phenomenon of Computer aided Designing, The Kind of flexibility,user friendliness it brings make it distinct from other softwares. There will be no alternative to AUTOCAD.

Eventually you cannot compare3D softwares with2D. They are runing on parallel paths.

3D softwares cannot justify AutoCAD and same2D cannot bring qualities of3D,

So in my opinnion both are going for long run.